Page 684 - V16 Catalogue Final

PROTECTION OF CABLES WITH FUSE LINKS

FUSE SELECTION FOR FIRE PUMP MOTOR STARTING

In some circuits such as the motors, significant transient overcurrents are produced during switching, and it is not economical
practice to match cable and fuse-link ratings. For these cases, the cable is chosen for the circuit load condition and the
fuse-links are chosen to withstand the transient overcurrent condition. The fuse-links provide only short-circuit current
protection to the motor, associated cables and other circuits components. The necessary overload protection is provided
by other means such as the motor starter’s thermal overload relay. The short-circuit protection of cables is covered by
Section 5 of AS/NZS 3008.1.1:1998 and the Table below shows how fuse-links relate to these requirements in protecting
V75 rated PVC insulated copper conductors.

Maximum Current-Carrying Maximum GEC, ABB or IPD
Capacity (A) Fuse-Link Rating (A)
Conductor
cross-sectional “Unenclosed” condition. “Enclosed” condition.
area (mm2) Ratings according to Ratings according to Type T DIN Type
Table 6, Column 6 of Table 6, Column 8 of ‘gG’ ‘gL’-’gG’
AS/NZS 3008.1.1:1998 AS/NZS 3008.1.1:1998
1 13 11 16 16
1.5 16 14 20 20
2.5 23 20 35 32
4 31 26 50 40
6 40 34 63 50
10 54 47 80 80
16 72 62 125 125
25 97 87 200 200
35 120 100 250 250
50 145 125 355 355
70 185 155 450 500
95 230 185 630 630
120 265 220 710 800
150 310 250 800 1000
185 355 285 1000 1000
240 425 340 1250 1000
300 490 390 1250 1000
400 570 455 1250 1000
500 660 530 1250 1000
630 760 620 1250 1000
1. Selection of the above fuse-links is based on the formula I t = K S given in Clause 5.3 of AS/NZS 3008.1.1:1998
2
2 2
where:
I = Current which causes the fuse-link to operate in 5 seconds.
t = 5 seconds.
K = Constant of 111 for PVC insulated copper conductor, for the condition of initial.
temperature 75°C and final temperature 160°C (during overcurrent condition).
S = Cross-sectional area of the conductor in mm . 2
2. For motor start fuse-links (i.e. those classified and marked ‘gM’) the larger of its dual current ratings is applicable,
e.g. 160A for TCP100M160 type.

676 V16-TR-R03 www.ipd.com.au Phone: 1300 556 601